HEREDITY

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HEREDITY

• BIG IDEAS
• Traits and Heredity
• Gregor Mendel
• Punnett Square
• Cross Pollination of Flowers

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WHO WAS GREGOR MENDEL?

• Mendel was a monk who taught science and
  performed many experiments.
• Mendel discovered the principles of heredity in
  the monastery garden.

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Unraveling the mystery

• Mendel worked with plants and knew that
  inheritance patterns were not always clear.
• EXAMPLE Sometimes a trait that appeared in one
  generation (parents) was not present in the next
  generation (offspring).
• BUT in the generation AFTER that the trait
  appeared.

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Self-pollinating peas

• Mendel chose pea plants.
• Pea plants were able to self-pollinate.
• A self-pollinating plant has both male and female
  reproductive structures

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SELF-POLLINATING PEAS

• Eggs (in an ovule) and sperm (in pollen) from the
  same plant combine to make a new plant.
• Mendel was able to grow true-breeding plants.
• When true-breeding plants self-pollinates, all of
  its offspring will have the same traits.
• EXAMPLE A true-breeding plant with purple
  flowers will have offspring with purple flowers.

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Cross-pollinating Peas

• Pea plants can also cross-pollinate.
• Cross pollination pollen from one plant
  fertilizes the ovule of a flower on a different
  plant.
• Pollen can be carried by insects to a flower on a
  different plant.
• Pollen can be carried by the wind from one
  flower to another.

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CHARACTERISTICS

• CHARACTERISTIC a feature that has different
  forms in a population.
• EXAMPLE Hair color, eye color, skin color.
• TRAITS The different forms of these
  characteristics.
• Mendel used different traits to study heredity.
• He chose purple flowers and white flowers.

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MIX AND MATCH

• Mendel used true breeding plants.
• He decided to find out what would happen if he
  bred, or crossed, two plants that had different
  traits.
• TO BE SURE THAT THE PLANTS CROSS-POLLINATED,
  MENDEL REMOVED THE ANTHERS SO THE PLANTS COULD
  NOT SELF-POLLINATE!
• Then, he used the pollen from another plant to
  fertilize the plant.

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MENDELS FIRST EXPERIMENT

• Mendel crossed purple flowers with white flowers.
• RESULTS All the offspring were purple.
• Dominant Trait Purple Flower
• Recessive Trait White Flower

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MENDELS SECOND EXPERIMENTS

• Mendel allowed the first-generation of plants to
  self-pollinate.
• The recessive trait of the white flower
  reappeared in the second generation.

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Ratios in mendels experiments

• The recessive trait did not show up as often as
  the dominant trait.
• Mendel decided to figure out the ratio of
  dominant traits to recessive traits.
• A ratio is a relationship between two different
  numbers that is often expressed as a fraction.
• Look at page 60 and calculate the ratios for each
  of those plants that Mendel crossed pollinated.

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I CAN STATEMENTS

• I can tell you that a recessive trait is
• I can tell you that a dominant trait is
• I can tell you what cross-pollination is
• I can tell you what true-breeding is
• I can tell you what a Punnett Square is
• GREAT JOB MY JUNIOR GENETICISTS!!! So proud of
  you!